Question and Answer Session from the AGRRI
Seminar, 25/11/2003, Network Rail, London
If you're looking to attend a workshop on
the New EMC Directive and
Technical Documentation for the Railway Industry, we're running one in
London on Wednesday, 4th June 2008 at the IET's Savoy Place.
The Advisory Group on Rail Research and Innovation (AGRRI) ran a
seminar, sponsored and organised by Network Rail, on ‘EMC in Railways: Who and How’
The seminar was a unique opportunity to learn from leading industry experts on
research and management in EMC and to influence how the industry's obligations
will be discharged. It also introduced Network Rail's emerging thinking
on EMC policy.
There will be a continuation of this discussion at EMC York 2004, in a dedicated ‘railways’ conference stream.
The question and answer session from the open forum has been
transcribed for your reference.
-
Q: How "unprotected" actually is the RF Spectrum? Do we
understand sufficiently, how for example the capture effect mitigates
against random noise transgressing a channel? -
Clive Avery, AEAT
-
A: The Radio Spectrum is a resource where frequency allocations
are managed at International level by the ITU. The ITU allocations are then
implemented at National level. The Radio Spectrum is protected from
interference by EMC Standards which set limits for unwanted radiated emissions.
Part of the lack of acceptance by the Radio community of EN50121-2 is that the
limits set are significantly higher than those set by accepted EMC standards -
50-60dB more! The Radiocommunications Agency commissioned York EMC Services Ltd
to investigate this. The results of the first contract appear on the YES
and RA [now OFCOM]
websites, the latest measurement results were presented as part of the AGRRI
seminar by Andy Rowell. The key issue is that the limits in EN50121-2 are set
at a level that can be measured at the trackside using conventional antenna and
spectrum analyser system with the analyser using a peak detector - hence
recording transient and continuous noise. The new measurement system described
allows the transient and continuous noise to be identified separately and
therefore the EN50121 limits can be adjusted to reflect the continuous noise
and therefore the continuous threat to the radio spectrum -
Chris Marshman, York EMC Services Ltd
-
Q: Why is the standard (GE/RT8015) limited to 2 GHz, when 3G coms & Bluetooth
use frequencies in the range of 2.4GHz? -
Dennis Stanley, Bombardier Transportation
-
A: GE/RT8015 covers a similar upper limit to the range as that covered in
EN50121. However you make a good point regarding newer technology. Perhaps both
sets of standards should be modified accordingly -
Jeff Allan, RSSB
-
Q: No mention so far of EN50155 - why has it not been included within the
EMC compliance process? -
Tony Barwell, TUV
-
A: EN50155 was one of the early standards for commonality of sourcing
for railway equipment in general. It covers environmental in addition to EMC
issues; those tests and limits, which fall within the preview of EN50121 are
harmonised with or similar to EN50121. It also includes requirements for
conducted interference emission and immunity outside of the frequency limits of
EN50121, and limits for tolerance of supply voltage variation. It tends to be
overshadowed by EN50121 as it does not carry the weight of an EU Directive as
does EN50121, but remains a valid and useful standard -
Clive Avery, AEAT
-
A. EN50121 actually calls up EN50155. It should be noted that the
requirements of EN50155 in terms of Surge are less onerous than EN61000-4-5
and much less onerous than the old RIA 12. -
Chris Marshman, York EMC Services Ltd
-
Q: In relation to plant & equipment using for eg 12/24vdc:
Can the production of the Technical file/safety case be made easier by
documenting some evidence on what criteria systems/components would give risk
of emitting/receiving unacceptable levels of EMC? -
John Ockenden, Carilion Rail
-
A: When compiling a TCF, the EMC data for the systems/components being
integrated into the final delivered system, should be obtained from the
manufacturer/supplier. This evidence is part of mitigating the risk and
demonstrating that the final system will be compliant, this will however depend
on the integration process and verification (EMC testing at system level) -
Chris Marshman, York EMC Services Ltd
-
Q: Is there an agreed industry wide approach to the EMC Directive
with respect to rolling stock?
Example: new telecoms equipment to be
fitted to rolling stock made up of CE marked units, is this a system or
installation? is a TCF required? for system or installation? -
Justin Caton, Development Engineer, HSBC Rail
-
A: Let us consider the example. New telecoms equipment should be
CE marked in relation to the R&TTE Directive. This equipment is being
procured for existing rolling stock. Considerations are that conformance to the
R&TTED does not necessarily mean that the equipment is robust from an EMC
point of view in the rolling stock environment, also how will the telecoms
equipment affect the EMC characteristics of the rolling stock and hence affect
its Safety Case? The telecoms apparatus manufacturer or the system integrator
should ensure that the apparatus has adequate immunity to operate
satisfactorily in the rolling stock environment. Assuming the out of band
emissions from the telecoms equipment meets appropriate limits and that the
equipment is installed using good practice, then the rolling stock emissions
are unlikely to be affected except at the transmission frequencies/bands of the
apparatus. The compatibility of such telecoms with the railway network should
have been undertaken prior to consideration of fitting the apparatus. In the
case of non-telecoms equipment eg an
OTMR
then the OTMR will have to comply
with the EMC Directive. It will be necessary to demonstrate that the OTMR is
suitable for use in rolling stock. An approach here would be to test to
EN50121-3-2 and present the results in a TCF, the OTMR can then be CE marked -
the TCF should provide generic installation guidance to enable the system
integrator to install the equipment. When installed it may be necessary to
verify that the emission characteristics of the rolling stock are unaffected
and therefore that the Safety Case is unaffected. This may be regarded as the
minimum approach for retrofitted equipment. An alternative valid view is that
it is the installed OTMR system that is being supplied and that this should
conform with the EMCD. This will require a TCF for the installed system and
will be generic for a number of vehicle fitments with verification measurements
performed on a representative example of rolling stock fitted with the OTMR -
Chris Marshman, York EMC Services Ltd
-
Q: Does the directive differentiate between "repair" and
"re-conditioning" equipment built before the directive came into
force? What about "re-conditioning" equipment built before the
directive came into force? Does this then require a TCF? -
Simon Jarrett, Angel Trains
-
A: The EMCD is not retrospective and so does not apply to
equipment built before 01/01/1996. It does not cover 'spares' and only applies
when equipment is 'first placed on the market or taken into service'. So,
repairs that restore equipment to its original specification are outside the
scope of the EMCD. Reconditioning is treated by the EMCD as manufacture. Where
reconditioning is entirely mechanical eg new seats etc and the electrical
systems are restored to the original specification, then reasonably this may be
considered in the same way as a repair, however when a major rebuild takes
place then this is the same as for new manufacture eg Brush Class 57. Where
reconditioning is accompanied by partial integration of new
electrical/electronics systems then these should be considered in the same way
as for the OTMR example given above, ie as a minimum the equipment being
installed should be CE marked as fit for the intended operating environment eg
on-board rolling stock -
Chris Marshman, York EMC Services Ltd
-
Q: In the light of the evidence shown in Andrew Rowell's
presentation, showing that RF emissions from the railway are shaped both by the
train and by the configuration of the traction supply system - and will also be
influenced by the number of trains in the area - how is responsibility for
emissions from the railway to the outside world, in accordance with the
requirements of the EMC directive, determined - does the infrastructure
controller have to take ultimate responsibility for the total emissions, as he
has control of:
a) design of infrastructure, including traction supply system.
b) number of trains he allows to operate in an area.
If so, he must also be responsible for emission
characteristics of the trains he allows onto his network -
David Bulgin, RSSB
-
A: The EMCD is intended to cover the supply of electrical/electronics
apparatus into the European market place. It is primarily targeted at
manufacturers and it is the responsibility of manufacturers to demonstrate
conformance with the essential protection requirements. So, for new rolling
stock it is clearly the manufacturer's responsibility to demonstrate
conformance and that it will conform when used in its intended operating
environment. It is the user's responsibility to ensure that he only takes into
service compliant equipment, in the case of rolling stock the TOC. There is
therefore some responsibility placed on the ROSCO to ensure that compliant
equipment is procured, depending on the contractual arrangements between TOC,
ROSCO and manufacturer. In order for the manufacturer to deliver compliant
equipment he needs to demonstrate that the protection requirements are met for
the environment, therefore the manufacturer needs to take account of the
infrastructure. The threats posed by the infrastructure to the rolling stock
and from the rolling stock to the infrastructure need to be identified and
mitigated against. This implies that the EMC details of the infrastructure are
available to the manufacturer. If not, the manufacturer can only rely on
published agreed standards ie EN50121-3-1. The threat to the outside world may
however be minimised by the number of trains operating in the area and this
would be a legitimate limitation on use specified within the TCF for the
rolling stock. So, the responsibility for new rolling stock does rest with the
manufacturer, the law however requires him to be duly diligent and this may be
limited by the availability of the EMC characteristics of the infrastructure.
The infrastructure controller does have responsibility for the emissions to the
outside world when he is responsible for making changes to the infrastructure
and in this instance the rolling stock is part of his environment with
limitations which must be taken account of when planning the changes.
Such changes should come under Network Rail’s EMC policy and the WCRM EMC
Assurance Guide -
Chris Marshman, York EMC Services Ltd
-
Q: EN50121 Part 4 should have become a free-standing harmonised
standard several years ago. Who is responsible for failing to get this
done? -
Donald Armstrong, Atkins Rail
-
A: This would be extremely helpful to many manufacturers.
I don’t know who is responsible for failing to get this done. I believe EN50121 is
being viewed as a package and therefore all of it needs to be adopted not just
a part -
Chris Marshman, York EMC Services Ltd
-
Q: The term 'excluded installation' as specified by UK SI 2372,
can the panel clarify that fixed installations are only excluded from the need
to CE Mark and NOT excluded from the need to meet the essential protection
requirements? -
David Atkey, ERA Technology
-
A: This is correct. The EMCD applies to installations, what is
excluded is the need to CE mark the installation. The installation should still
meet the protection requirements -
Chris Marshman, York EMC Services Ltd
-
Q: As a supplier of IT and telecommunications equipment not
specifically designed for railway use, do the panel conclude that a TCF is
required when the directives specifically exclude fixed installations, and the
new directives go to great lengths to clarify this position? -
Mark Brooke, Marconi
-
A: The old chestnut! COTS equipment when integrated into equipment
for railway use should conform with the appropriate directives for the intended
operating environment ie a railway. This will require the use of TCFs in many
instances, for example, when equipment is within 3m of the rails or when EN50121
is being used to demonstrate conformance. As stated in the previous question
the so-called excluded installation is only excluded from the conformity
assessment procedure. The new EMCD doesn’t exclude fixed installations either
it only excludes them from being CE marked, it does however require that the
installer/user of such a fixed installation is able to demonstrate that the
equipment meets the protection requirements. As the new EMCD is not likely to
be effective until 2007-8, Marconi is required in the meantime to comply with
the existing EMCD and where COTS equipment is being integrated it is subject to
further manufacture and is therefore within the conformity assessment regime ie
it must be CE marked -
Chris Marshman, York EMC Services Ltd
-
Q: How does NR audit/police EMC compliance requirements with relation to
procurement of equipment installed on NR infrastructure? -
Dominic Kelsey, Rail Link Enterprise
-
A: Evidence for the achieved EMC for new installations, upgrades and
modifications is provided as part of their acceptance case. Currently, NR
has no coherent policy of acceptance of different infrastructure products on
the network. Approvals of signalling equipment has been following the
process in NR Code of Practice RT/E/S10071 'Approval of signalling equipment'
Issue 1 of December 1997 which requires that EMC with existing railway systems
and equipment is achieved. Often, functional testing is taken as proof that EMC has been achieved –
Maya Petkova, Network Rail
-
Q: As railway infrastructures are fixed, have known characteristics,
can be tested in labs and protected by filters and screening why is there not
more emphasis on reducing susceptibility limits, rather than worrying about
train emissions. Every time a new train is built/designed it will need
extensive expensive trialling. A moving train EMC profile will
deteriorate far quicker than static infrastructure -
Geoff Eggrison, Marconi
-
A: New technology being introduced is generally more immune to EM
interference. In addition, all signalling product upgrades are tested for
immunity as per EN50121, which has more onerous requirements. There is
still a strongly defined need for a thorough compatibility assessment with
trains and other systems, which is performed in accordance with the principles
set out by EN50238. Recent projects that applied its principles include
SSI and compatibility with Class 390 train that was accepted without a clearly
defined safety margin but on the basis of the results of monitoring and the
assertion of the robust design of SSI. It is important to remember that
any EMC argument is time limited and only valid at the time of acceptance and
the EM environment is evolving all the time -
Maya Petkova, Network Rail
-
Q: To what extent should a Contractor show due diligence for EMC
compliance, including satisfying the safety case, when designing, assembling, installing
on the NR infrastructure various sub-systems interlinked in modular
format? The modules, in turn, contain items of equipment and components
in their own right -
Raymond J Leach, Network Rail
-
A: The top level requirements for EMC in terms of safety and
corresponding safety cases is contained within GE/RT8015 -
Maya Petkova, Network Rail
-
A: The WCRM EMC Assurance Guide provides the guidance needed -
Chris Marshman, York EMC Services Ltd
-
Q: What is the responsibility of NR in providing suitable
guidance to contractors where they are contracted to introduce new
sub-systems on to the infrastructure? -
Raymond J Leach, Network Rail
-
A: By adopting the EMC Policy as presented at the EMC Seminar, NR
should make sure that EMC requirements in accordance with GE/RT8015 are part of
the procurement contract. Evidence that analyses to the depth required by
GE/RT8015 should be presented in the safety cases. This may be test results, or
results from modelling, as appropriate (e.g. regarding safety targets
requirements results from modelling can be confirmed over time in operation, as
accumulated) -
Maya Petkova, Network Rail
-
A: The WCRM EMC Assurance Guide provides the guidance needed here
- Chris Marshman, York EMC Services Ltd
-
Q: Would a Competent Body be required to assess the evidence of EMC if
the standards and TCF route is followed, and if so, would this be a joint
responsibility between NR and subcontractor? -
Raymond J Leach, Network Rail
-
A: NR as infrastructure controller is ultimately responsible for
conformity to the protection requirements of the EMC Directive. The TCF
route should be followed to demonstrate compliance with EN50121 (the harmonised
European standard for railways) and the assessment of Competent Body sought
since EN50121 is not in the OJEC. It is important that this
responsibility is assigned to the responsible contractor during design and
installation stage and all relevant measures adequately recorded in the EMC
Project File. By accepting the EMC Project File, NR effectively satisfies
the protection requirements and agrees that the applied EMC standard is
appropriate, i.e. demonstrates due diligence has been applied as far as this
part of the lifecycle process is concerned -
Maya Petkova, Network Rail
-
A: The WCRM EMC Assurance Guide provides the guidance needed
here -
Chris Marshman, York EMC Services Ltd
-
Q: EMC Directive states that fixed installations are excluded (Maya Petkova
morning presentation). Traction sub-stations are inherently fixed in
nature (apart from circuit breaker operations), so would these types of
sub-systems being introduced to the NR infrastructure be exempt? -
Raymond J Leach, Network Rail
-
A: The equipment/systems within the sub-station should all comply
with the EMCD. The sub-station is an excluded installation, again excluded from
the CE marking regime but not excluded from the protection requirements.
Sub-stations are addressed by the WCRM EMC Assurance Guide, where it is
expected that a Technical File (equivalent of a TCF but not a legal requirement)
will be prepared to cover the sub-station. This file should be assessed by a Competent Body
- again this is not a legal requirement -
Chris Marshman, York EMC Services Ltd
-
Q: The application of the maximum allowable train emissions of
more than 50% of the normal level will be generally impossible to apply.
In most cases a single fault condition will have a much greater effect on the
allowable level than 50%, for example rail breaks in track circuits, or cable
faults on lineside systems. The problem then remains - what is the
acceptable level of fault analysis that needs to be carried out? That
will be the dominating factor. Any comment? -
Adrian Hines, A Hines Engineering Ltd
-
A: There is a similar problem with emissions from trains. Train
builders need to consider faults, which could increase emissions. Generally,
emissions are held to a tight level compared with normal values by means
of fault analysis and management of those faults. The same process is being
sought from infrastructure designers and maintainers. Therefore
the question is: can something be done to control these faults?
If not, the standard allows
agreement between the infrastructure controller and all train operators using
that section of track to a different agreed allowable level e.g. 10%. In this
way at least all parties would agree that nothing could be done to reach an
allowable level of 50% or better -
Jeff Allan, RSSB
-
Q: Why is the margin between minimum per train infrastructure
susceptibility (normal conditions) and maximum allowable per train emissions
set at 50 % (at best), ie 6dB total (at best) in fig. 1 of GE/RT8015? -
Dick Wall, Alstom TIS
-
A: I would not argue strongly if someone stated it should be 30%
or 70%. What is clear is that it should not be 90% - there is too little
allowance for faults and degradations nor should it be 10% - in this case the
system is too sensitive and putting too much burden on train operators having
to tightly control emissions, while not providing infrastructure which is
properly engineered to counter emission threats. For older infrastructure (the
majority) there is always the option of the infrastructure controller agreeing
a different level to 50% with all train operators using that section of track -
Jeff Allan, RSSB
-
Q: The 25 kV overhead is resonant at many frequencies. For
example, 3.8MHz at one site. Does the approach presented by Andy Rowell find
these? What is the bandwidth for the 360MHz timeplot? -
Donald Armstrong, Atkins
-
A: The new measurement system does show the effect of resonances
quite clearly. In the example presented showing a Class 91 on the ECML, it is
observed that the the maximum emissions occur some time before the train passes
the antenna and again that the emissions rise as the train moves further away.
What we don't yet know is whether the levels measured are independent of
antenna position. This work is currently drawing to a close and a new
sponsor is sought to continue the research so that we can consider further
areas such as resonance -
Chris Marshman, York EMC Services Ltd
Last Updated: 2008-Apr-18
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